1. Technical Field
The present invention relates to a quantum interference device, an atomic oscillator, an electronic apparatus, and a moving object.
2. Related Art
As an oscillator having high-accuracy oscillation characteristics on a long-term basis, an atomic oscillator is known which oscillates on the basis of energy transfer of atoms of an alkali metal such as rubidium or cesium (for example, see JP-A-2001-339302).
In general, an operating principle of the atomic oscillator is classified broadly into a method using a double resonance phenomenon based on light and microwaves and a method using a quantum interference effect (CPT: coherent population trapping) based on two types of light beams having different wavelengths. However, the atomic oscillator using a quantum interference effect can be made smaller than the atomic oscillator using a double resonance phenomenon, and thus has been recently expected to be mounted to various devices.
For example, as disclosed in JP-A-2001-339302, the atomic oscillator using a quantum interference effect includes a gas cell in which gaseous metal atoms are sealed, a semiconductor laser that irradiates the metal atoms in the gas cell with a laser beam including two types of resonance light beams having different frequencies, and a photodetector that detects the laser beam having passed through the gas cell. In such an atomic oscillator, an electromagnetically induced transparency (EIT) phenomenon occurs in which both of the two types of resonance light beams pass without being absorbed into the metal atoms within the gas cell when a frequency difference between the two types of resonance light beams has a specific value. The photodetector detects an EIT signal which is a sharp signal generated in association with the EIT phenomenon.
In addition, the atomic oscillator includes a heater that heats the gas cell, and a coil that generates a magnetic field in a direction along the axis of the laser beam in the gas cell. The gas cell is heated by the heater so that the alkali metal within the gas cell is maintained in a gaseous state having a desired concentration. In addition, Zeeman splitting occurs due to the magnetic field, and thus it is possible to improve a resolution by widening a gap between different energy levels at which the atoms of the alkali metal within the gas cell degenerate. As a result, it is possible to increase the accuracy of an oscillation frequency of the atomic oscillator.
Incidentally, in order to reduce the power consumption of the atomic oscillator, a power supply voltage is required to be decreased. However, in the heater, a current is increased by a decrease in a voltage so that power supplied to the heater does not change. For this reason, a magnetic field generated due to electrical conduction to the heater is increased, and the magnetic field acts within the gas cell, and thus an adverse effect such as a decrease in the accuracy of the oscillation frequency of the atomic oscillator is exerted. Meanwhile, such a problem is the same as in the atomic oscillator using a double resonance phenomenon based on light and microwaves.